UC San Diego

Bifidobacteria are gram-positive prokaryotes that contribute to a healthy gut microbiome and are known to play important roles in conferring health benefits to the host. Yet, very little is known about the mechanisms behind these probiotic effects. In this study, we identified transport systems and substrates within three distinct Bifidobacterium species: a probiotic strain found in the distal gut (B. longum), a probiotic strain found in breast milk and the gut (B. animalis), and an opportunistic pathogen found in dental caries (B. dentium). Transport systems characteristic of each species were tabulated and then compared. We found that B. longum and B. dentium have carbohydrate and MDR transporters that reflect their diametric environmental locations in the gastrointestinal tract (GIT). B. dentium and B. animalis share acid resistance systems to survive in their low pH environments (the oral cavity for B. dentium and breast milk for B. animalis). In addition, we discovered an abundance of vitamin transporters in B. longum which may explain some of its proposed probiotic effects. Finally, the GadBC system for gamma-aminobutyrate production and secretion was found only in B. dentium, confirming several studies that suggest that this oral pathogen may have the potential to confer probiotic effects in the gut. The results indicate that the transportome of each species reflects adaptation to its ecological niche and reveal distinguishing features of each strain, which provide the basis for future industrial and medical applications of beneficial bacteria.